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Changed rendering (and evaluation) behaviour in APEX 4.2

Today we ran into a problem in our recently upgraded APEX environment. In one of the pages we had a report defined on a pipelined table function. This function also changed a package global variable. The value of that global variable is used as a source for a page item that shows up in the same region just below the report. This ran fine in 4.1, it runs fine when we set the "Compatibility Mode" to 4.1 as well. But if we set that mode to 4.2...the page item shows...nothing !!!

What happened? According to the help on that Compatibility Mode property, items (and regions) in a display point are evaluated before rendering that display point. This is done to find out whether items / regions are displayed or not - to support the grid layout. To dig a little deeper (thanks to Patrick Wolf, who was helping us with this issue): As soon as the region grid is calculated, the same is done for the page item grid in the region which gets painted next. This calculation also has to determine the page item values, because they could be used in a condition of one of the following page items. This is all done before the region source is actually executed.

So, in our case, the value of the page item - what was based on the result of the pipelined table function - was evaluated before that pipelined table function was actually executed...and therefore returned null. We could easily spot that in the debug output: When we compared the order of evaluations of the region and the items we saw a (huge) difference in 4.1 and 4.2 mode.

So now we know what caused the issue. But how to solve it?
We created a PL/SQL sub region to the reports region and moved the page item to that subregion. That was not enough to evaluate the page item value after running the report. So we removed the PL/SQL source of that page item and moved it to the source of it's PL/SQL region. Even that didn't work out. But when we set the Item Display Position to "Below Content", we - finally - saw that the item was evaluated and rendered in the right position of the complete page flow....

So when you notice - similar - strange behaviour when running your upgraded pages in 4.2, it is worthwhile to check the difference in evaluation and rendering order is the cause of that!

Until we had the IG, we showed the data in a report (Interactive or Classic). Changes to the data where made by popping up a form page, making changes, saving and refreshing the report upon closing the dialog. Or by clicking an icon / button / link in your report that makes some changes to the data (like changing a status) and ... refresh the report.
That all works fine, but the downsides are: The whole dataset is returned from the server to the client - again and again. And if your pagination size is large, that does lead to more and more network traffic, more interpretation by the browser and more waiting time for the end user.The "current record" might be out of focus after the refresh, especially by larger pagination sizes, as the first rows will be shown. Or (even worse) while you…

Nowadays Docker is everywhere. It is one of the main components of Continuous Integration / Continuous Development environments. That alone indicates Docker has to be seen more as a Software Delivery Platform than as a replacement of a virtual machine.

However ...

If you are running an Oracle database using Docker on your local machine to develop some APEX application, you will probably not move that container is a whole to test and production environments. Because in that case you would not only deliver a new APEX application to the production environment - which is a good thing - but also overwrite the data in production with the data from your development environment. And that won't make your users very excited.
So in this set up you will be using Docker as a replacement of a Virtual Machine and not as a Delivery Platform.
And that's exactly the way Martin is using it as he described in this recent blog post. It is an ideal way to get up and running with an Oracle database …

If you created your own "updatable reports" or your custom version of tabular forms in Oracle Application Express, you'll end up with a query that looks similar to this one:
then you disable the "Escape special characters" property and the result is an updatable multirecord form.
That was easy, right? But now we need to process the changes in the Ename column when the form is submitted, but only if the checkbox is checked. All the columns are submitted as separated arrays, named apex_application.g_f0x - where the "x" is the value of the "p_idx" parameter you specified in the apex_item calls. So we have apex_application.g_f01, g_f02 and g_f03.
But then you discover APEX has the oddity that the "checkbox" array only contains values for the checked rows. Thus if you just check "Jones", the length of g_f02 is 1 and it contains only the empno of Jones - while the other two arrays will contain all (14) rows.
So for processing y…